Electrical pick-up for musical instruments



P 5, 1956 J. w. M BRIDE ELECTRICAL PICK-UP FOR MUSICAL INSTRUMENTS Filed April 21, 1951 IN V EN TOR.

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J A 7'7'0Q/VEY- United States Patent ELECTRICAL PICK-UP FOR MUSICAL INSTRUMENTS John W. McBride, Burbank, Califi, assignor to Bantar, Incorporated, Burbank, Califi, a corporation of California Application April 21, 1951, Serial No. 222,230 10 Claims. (Cl. 84-1.15)

This invention relates to pick-up devices for converting musical vibrations into electrical impulses. Such devices are now commonly utilized in connection with stringed instruments in which the strings are made of magnetic material, such as steel. The vibrations of the strings cause corresponding variations in the magnetic field of a permanent magnet; and electrotnotive forces corresponding to the variations are generated in a well-known manner in a coil through which the magnetic flux passes.

It is one of the objects of this invention to provide a simple and improved form of pick-up device.

It is another object of this invention to provide a device of this character which utilizes few parts and that is readily and easily installed.

It is still another object of this invention to provide a compact device of this character that is capable of providing a multiple unit adapted to cooperate effectively with a plurality of parallel strings.

It is another object of this invention to provide a bridge structure for the strings, that may readily be adjusted to bring the strings individually into proper relative position.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of several embodiments of the invention. For this purpose there are shown a few forms in the drawings accompanying and forming part of the present specification. These forms will now be described in detail, illustrating the general principles of the invention; but it is to be understood that this detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

Figure 1 is a fragmentary plan view of a musical instrument in which the invention is incorporated;

Fig. 2 is an enlarged plan view of a portion of the instrument illustrating the arrangement of the pick-up device;

Fig. 3 is a sectional view taken along a plane to correspond to line 3-3 of Fig. 2;

Fig. 4 is an enlarged sectional view taken along a plane corresponding to line 4-4 of Fig. 2;

Fig. 5 is a pictorial view of a modified form of pick-up device; and

Fig. 6 is a fragmentary sectional view taken along a plane corresponding to line 66 of Fig. 5.

In the present instance, the body 1 of the musical instrument may be made of wood or other suitable material. Strings 2, 3, 4, 5, 6, and 7 (made from magnetic material, such as steel), extend longitudinally of the instrument, and in general parallel relationship. The right hand ends of the strings are anchored by the aid of a bar 8, supported on the body 1.

Bridge structures 9, 10, and 11 are arranged transversely of the pairs of strings 2 and 3, 4 and 5, and 6 and 7. Bridge structure 9, similar to the others, is illustrated most clearly in Fig. 4. It includes a post 12 having a threaded shank 13 which is threaded into the body 1.

This post has a through threaded aperture 14, the axis of the aperture being transverse to the strings 2 and 3. Threaded into opposite ends of the aperture 14 are the headless screws 15 and 16. Each of these screws has a V-shaped slot 17 and 18 serving as a seat for the respective strings 3 and 2. By adjusting the positions of the screws 15 and 16 within the post 12 the relative spacing of the strings 2 and 3 can be varied. The adjustment may be made in one-half turn increments, whereby the slots 17 and 18 are kept in alignment with the strings 3 and 2.

Clamping nuts 19 and 20 are threaded respectively upon screws 15 and 16 and are turned so that one side of each nu-t engages the corresponding face of the post 12. These nuts may be knurled for convenient manipulation.

The pick-up device includes a permanent magnet 21 3) having upwardly extending polar projections 22, 23, 24, and 25. These projections form alternately south and north poles. The intermediate projection 23, forming a north pole, extends upwardly between the strings 6 and 5. Similarly, the interm diate projection 24, forming a south pole, extends upwardly between strings 4 and 3. The end projection 22, forming a south pole, extends upwardly to the left of string 7. The opposite end projection 25, forming a north pole, extends upwardly to the right of the string 2.

The permanent magnet 21 is embedded in a supporting member 26, which may be in the form of a plastic extending around the magnet 21 as well as lower portions of the projections 22 to 25. This plastic may be accommodated in a recess 34, formed in the upper surface of the body 1.

Between strings '7 and 6 a short cylindrical member or core 27 of magnetic material is disposed, its opposite polar ends facing the strings 7 and 6. Similarly, cylindrical magnetic members 213 and 29 extend respectively between strings 5 and 4 and strings 3 and 2. These members extend through pick-up coils 3 31 and 32. These pick-up coils thus surround the magnetic members 27, 23, and 29 and the lower portions of these coils 30, 31 and 32 may be embedded in the supporting means 26.

The permanent magnet 21, together with the magetic members 27, 28, and 29, form a magnetic circuit. Variations in the magnetic flux passing through the members 27, 28, and 29 cause the generation of corresponding electromotive forces or electrical impulses in the coils 30, 31 and 32, which impulses may be amplified in a well-known manner. The amplified effects may then be properly utilized to convert these electrical impulses into sound.

The vibration of the strings 2, 3, 4, 5, and 6 causes these variations in magnetic flux in a well known manner.

By appropriate adjustment of the screws 15 and 16, the spacing of the strings 2, 3, 4, 5, and 6 with respect to opposed polar areas may be readily adjusted to conform to the desired vibration efiects. The slots 17 and 18 of screws 15 and 16 open in the direction parallel to the axis of the cores 27, 28, and 29. Accordingly, vibration of the strings toward and away from their respective cores is not materially damped. Thus, the particular bridge structures materially enhance tone duration.

In the modified forms of Figs. 5 and 6, a cylindrical support 33 of non-magnetic material, such as wood or plastic, is utilized. This support may be appropriately supported on the body 1 to extend transversely of the strings 35, 36, 37, 38, 39, and 40. These strings are made of magnetic material such as steel.

The support 33 has a longitudinal through aperture 41. The support 33 has appropriate transverse through openings 42, intersecting the opening 41, through which openings the strings 35 to 40, inclusive, respectively pass.

Pick-up coils 43, 44, and 45 are disposed in annular grooves 46, formed on the support 33. within aperture 41 are disposed a set of magnetic members or cores, such as short cylinders 47, 48, etc. The coils 43, 44, and 45 respectively surround these magnetic members 47, 48, etc.

Extending through other transverse openings are the magnetic cylindrical members 49, 50, 51, and 52. These cylindrical members form a second set of members to define a magnetic circuit. The strings 35 to 40 inclusive pass between the adjacent polar surfaces of the magnetic members, as illustrated most clearly in Fig. 6.

One of the sets of the magnetic members may be in the form of permanent magnets. Thus either the cylindrical core members 47, 48, etc., may be made of permanent magnets, or else the cylinrical members 49, t 51, and 52 may be formed of permanent magnets. in either case, vibrations of the strings to cause a generation of electrical impulses in the pick-up coils 43, 44, and 45.

The inventor claims:

1. In a device for translating vibrations of a plurality of independently vibratory parallel strings into electrical impulses: a plurality of spaced coils, the axes of the coils falling substantially on a common line; and a magnetic circuit including, as elements, magnetic members respectively within the coils, and a plurality of magnetic means exterior of the coils and interspaced between the coils and defining air gaps between each end of said members and said means; at least some of the elements being permanent magnets.

2. In a device for translating vibrations of a plurality of independently vibratory parallel strings into electrical impulses: a plurality of spaced coils, the axes of the coils falling substantially on a common line; and a magnetic circuit including, as elements, magnetic members respectively within the coils, and a plurality of magnetic means exterior of the coils and interspaced between the coils and defining air gaps between each end of said members and said means; said magnetic means being a permanent magnet having alternate north and south polar projections, said projections being disposed on opposite sides of the ends of the magnetic members.

3. In a device for translating vibrations of a plurality of parallel strings into electrical impulses: a non-magnetic support having a plurality of laterally spaced annular recesses, as Well as an aperture extending substantially axially through the support and substantially aligned respectively with the axes of all of the recesses; coils respectively mounted in the recesses; said support having through openings transverse to the aperture; and a magnetic circuit including as elements, a first set of magnetic members disposed in the aperture and in spaced relation, the members respectively being disposed within the coils; said magnetic circuit having a second set of magnetic members disposed in the openings, at least some of the magnetic members being permanent magnets; said strings being adapted to extend through the spaces between the adjacent magnetic members.

4. In a device for translating vibrations of a plurality of parallel strings into electrical impulses: a non-magnetic support having a longitudinal aperture; coils mounted on said support and encompassing the aperture; said support having through openings transverse to the aperture; and a magnetic circuit including as elements, a first set of magnetic members disposed in spaced relation, the members respectively being disposed within the coils; said magnetic circuit having a second set of magnetic members disposed in the openings and between adjacent ends of the members of the first set; at least some of the magnetic members being permanent magnets; said strings being adapted to extend through the spaces between adjacent magnetic members.

5. In a device for translating vibrations of a plurality of parallel strings into electrical impulses: a non-magnetic support having a longitudinal aperture; coils mounted on said support and encompassing the aperture; said support having through openings transverse to the aperture; and a magnetic circuit including as elements, a first set of magnetic members disposed in spaced relation, the members respectively being disposed within the coils; said magnetic circuit having a second set of magnetic members disposed in the openings and between adjacent ends of the members of the first set; the first set of magnetic members being permanent magnets; said strings being adapted to extend through the spaces between adjacent magnetic members.

6. In a structure for positioning a pair of strings for a musical instrument: a post having a through threaded aperture; a pair of screws, each having a transverse slot for the reception of a string, and respectively threaded into the opposite ends of the aperture; and nuts threaded on the screws and engaging opposite faces of the post.

7. In a stringed musical instrument: a body having a top surface; a plurality of substantially parallel strings; a plurality of spaced coils, the axes of the coils falling substantially on a common line, said axes extending across said surface; a magnetic circuit including, as elements, magnetic members respectively within the coils, and magnetic means exterior of the coils for defining air gaps between each end of said members and said means; and a supporting structure for said strings, and mounting said strings in spaced substantially parallel relation along said surface and between said means and said members respectively, said strings extending transversely of said axes, said supporting structure including means providing slots receiving said strings, the slots extending parallel to the strings respectively and opening in a direction substantially parallel to said axes of said coils.

8. In a device for translating vibrations of a plurality of independently vibratory parallel strings into electrical impulses: a plurality of spaced coils, the axes of the coils falling substantially on a common line; and a magnetic circuit including, as elements, magnetic members respectively within the coils, and a plurality of magnetic means exterior of the coils and interspaced between the coils and defining air gaps between each end of said members and said means.

9. In a stringed musical instrument: a body having a top surface; a plurality of substantially parallel independently vibratory strings; a plurality of spaced coils, the coils being respectively between adjacent strings, the axes of the coils all falling substantially on a common line, and transverse to the strings; a plurality of posts carried by the body; an adjusting screw for each post, each of said screws being adjustably carried by the posts for movement in a direction substantially parallel to the axes of the coils, each screw having a transverse slot in the end thereof receiving the strings respectively.

10. In a device for translating vibrations of a plurality of substantially parallel strings into electrical impulses: an elongate support having an aperture extending longitudinally thereof, said support having a plurality of peripheral recesses spaced longitudinally along the support; a plurality of pick-up coils mounted in the peripheral recesses respectively; and a plurality of magnetic members in the aperture and forming cores for the coils respectively; said support having transverse openings intersecting said aperture for passage of said strings.

References Cited in the file of this patent UNITED STATES PATENTS 1,852,795 Wegel Apr. 5, 1932 1,900,038 Bower Mar. 7, 1933 1,906,985 Marrison May 2, 1933 1,976,384 Braman Oct. 9, 1934 2,175,325 Sunshine Oct. 10, 1939 2,262,335 Russell Nov. 11, 1941 (Other references on following page) 5 Liske Aug. 4, 1942 Briderman July 13, 1943 Fender et a1 Dec. 7, 1948 Cousineau Aug. 22, 1950 Smith Oct. 3, 1950 5 McCarty Sept. 11, 1951 6 Martin Sept. 25, 1951 Fender Oct'. 30, 1951 Melita Jan. 20, 1953 FOREIGN PATENTS Great Britain May 15, 1947 

